International Society for Industrial Process Tomography

Volume Fraction Estimation in Pneumatic Conveying from Tomographic Measurements

T. Suppan¹, M. Neumayer¹, T. Bretterlieber¹ and S. Puttinger²

¹Institute of Electrical Measurement and Measurement Signal Processing, Inffeldgasse 23/II,
A-8010 Graz, Austria, Graz University of Technology

²Department of Particulate Flow Modelling, Johannes Kepler University Linz,
Altenbergerstrasse 69, A-4040, Linz, Austria

^*Email: neumayer@tugraz.at

ABSTRACT

Pneumatic conveying is a standard technique for the transport of particulate and granular materials. In pneumatic conveying the material is transported by means of a gas stream through a pipe system. Flow metering in pneumatic conveying is a difficult measurement problem and requires non-invasive measurement techniques. The spatial dependence of the material density and the stream velocity, requires a volumetric measurement principle. In this paper we analyze the capability to estimate the volume concentration factor from capacitive sensing data using electrical capacitance tomography. In particular, we investigate the capability of back-projection type imaging algorithms. The ill-posed nature of the imaging problem of ECT requires the incorporation of prior knowledge in the design of the estimator. We analyze the different flow profiles in pneumatic conveying for horizontal and vertical pipes and present the construction of sample based priors. Based on an ensemble of prior samples we show the incorporation into back-projection type estimators by different techniques, e.g. Gaussian summary statistics, or state reduction techniques. We discuss the construction of different linear image reconstruction algorithms and present a framework, which allows a detailed statistical analysis of the performance of the different estimators. We analyze different algorithms and scenarios including an analysis of the robustness, where the true flow profile differs from the prior assumption. Based on scatter plots we demonstrate, that the incorporation of specific prior knowledge leads to proper estimator behavior, e.g. reduced variance, making ECT a suitable tool for the estimation of the volume concentration factor.

Keywords Pneumatic conveying, electrical capacitance tomography, void fraction estimation

Industrial Application General